1. Field of the Invention
The present invention generally relates to an automatic television-camera supervisory system. More particularly, the invention is directed to an automatic television-camera supervisory system which is adapted for monitoring an area of interest by taking a video image thereof using a television camera and reproducing the video image on an image screen of a television receiver monitor, and which is capable of detecting abnormalities occurring in the area being monitored.
2. Description of the Related Art
Heretofore, a so-called television supervisory system is composed of a television camera and a television receiver monitor, wherein a watchperson monitors an area of concern for the occurrence of an abnormality, such as an unauthorized approach or entry in the area, by watching a video image generated on the screen of the television receiver. Such a television-camera supervisory system is disadvantageous with respect to man-power and labor because the system requires the continuous attendance of a watchperson who is in charge of watching the television monitor. Recently, a supervisory system has been developed and adopted for practical applications which does not require the continuous attendance of a watchperson, but which instead calls for confirmation by the watchperson only when a possible abnormality has been detected. More specifically, the occurrence of an abnormal event in an area of interest is detected by a sensor, whereon a video image of the area associated with the sensor is picked up by a television camera to be reproduced on a screen of a television receiver for confirmation by the watchperson.
As noted above, the first mentioned supervisory system is disadvantageous with respect to labor requirements since a watchperson must always be attendant at a location where the television receiver monitor is installed for watching the scene generated on the screen thereof. In this respect, the second mentioned supervisory system is preferred over the former, because attendance and confirmation by the watchperson are called for only when an abnormality is detected by a sensor and a corresponding scene is generated on the television screen. However, the sensor used in the second mentioned supervisory system is typically constituted by an infrared ray sensor system which suffers drawbacks. First, because a light beam travelling in a straight line is made use of in the infrared sensor system, a predetermined face-to-face orientation must always be maintained between an infrared beam transmitter and a beam receiver. For this reason, a limitation is unavoidably imposed on the sensor area or the area to be monitored which is dependent on the availability of a place for installation of the light beam transmitter and the beam receiver. Thus, a difficulty is often encountered in the abnormality monitoring of a desired area. Second, the coverage of the infrared light beam is generally on the order of two or three hundred meters. In other words, the infrared sensor system is also limited with respect to coverage. Further, more than a minor expense is involved in installing the sensors and wiring the required electrical connections.